1. Field of the Invention
The present invention relates to a wheel supporting device in which a hub spindle of a hub wheel on which a wheel is mounted and an outer ring of a constant velocity joint are torque-transmittably coupled to each other.
2. Related Art
As a wheel supporting device of this type, a device is known in which a hub spindle of a hub wheel and an outer ring of a constant velocity joint are coupled by a coupling bolt, and opposite side face splines adapted to mesh with each other are respectively formed on an end face of the hub spindle of the hub wheel and on an end face of the constant velocity joint which is abutted against that end face. The hub wheel and the constant velocity joint are torque-transmittably coupled to each other by these opposite side face splines (e.g., refer to JP-A-63-184501).
As a wheel supporting device of this type, a device is known in which, as shown in FIG. 12, to torque-transmittably couple a hub wheel 210 and a constant velocity joint 250, opposite side face splines 218 and 262, which are adapted to mesh with each other to transmit torque between the hub wheel 210 and the constant velocity joint 250, are respectively formed on an end face of a hub spindle 213 of the hub wheel 210 and on an end face of a side wall portion 261 of an outer ring 260 of the constant velocity joint 250 which is abutted against that end face.
In addition, as a wheel supporting device of this type, a coupling bolt 270 is projected from the end face of the side wall portion 261 of the outer ring 260 of the constant velocity joint 250, and an externally threaded portion 273 of a leading end of a shank 272 of this coupling bolt 270 is inserted into an inner hole 214 of the hub spindle 213 from one end side thereof (central side in the transverse direction of the vehicle) toward the other end side thereof (outer side in the transverse direction of the vehicle). In a state in which this externally threaded portion 273 is projected from the other end side of the inner hole 214 of the hub spindle 213, a lock nut 275 is tightened against the externally threaded portion 273, thereby integrally coupling the hub wheel 210 and the constant velocity joint 250.
In the wheel supporting device having the structure such as the one shown in FIG. 12, owing to an annular gap between the inner hole 214 of the hub spindle 213 and the shank 272 of the coupling bolt 270, it is difficult to perform centering between the hub wheel 210 and the constant velocity joint 250, and the meshing between the opposite side face splines 218 and 262 is troublesome.
In addition, in the state in which the hub wheel 210 and the constant velocity joint 250 are integrally coupled by the coupling bolt 270 and the lock nut 275, it is conceivable that, owing to the annular gap between the inner hole 214 of the hub spindle 213 and the shank 272 of the coupling bolt 270, the hub wheel 210 and the constant velocity joint 250 can vibrate relative to each other, or abnormal noise can occur.
Accordingly, it is conceivable to fit the inner hole 214 of the hub spindle 213 and the shank 272 of the coupling bolt 270 with a slight gap by fabricating the inner hole 214 of the hub spindle 213 and the shank 272 of the coupling bolt 270 with high accuracy. However, if the inner hole 214 of the hub spindle 213 and the shank 272 of the coupling bolt 270 are fabricated with high accuracy, the fabrication cost becomes high, and the insertability of the shank 272 of the coupling bolt 270 with respect to the inner hole 214 of the hub spindle 213 deteriorates.
Further, as shown in FIG. 12, an inner ring 221 of a rolling bearing 220 is insertedly fitted on an outer peripheral surface of the hub spindle 213 of the hub wheel 210, a tubular spindle-shaped spindle end portion of the hub spindle 213 is calked toward an end face (radially outward) of the inner ring 221 to form a calked portion 217, thereby fixing the inner ring 221 to the outer peripheral surface of the hub spindle 213.
It is a difficult operation to form the side face splines 218 on the end face of the calked portion 217 by forging while ensuring concentricity after the inner ring 221 of the rolling bearing 220 has been assembled onto the outer peripheral surface of the hub spindle 213 of the hub wheel 210 by means of the calked portion 217.
Further, when the side face splines 218 are formed by forging, an axial compressive force acts on the inner ring 221, thereby possibly exerting an adverse effect on a raceway surface 222 of the inner ring 221.
Furthermore, also in the inspection of quality assurance of the side face splines 226 formed on the calked portion 217 of the hub spindle 213, the inspection has been troublesome since it has to be performed in a state in which the rolling bearing 220 including the inner ring 221 is assembled on the hub spindle 213.
Moreover, if the hub wheel and the constant velocity joint are torque-transmittably coupled to each other by the meshing of the opposite side face splines on the end face of the hub spindle of the hub wheel and on the end face of the constant velocity joint, there is a possibility of ingress of foreign matters such as muddy water and dust into the interior from a gap between meshing portions of these opposite side face splines, resulting in the development of rust.